Voltage regulator



12, 1953 D. A. WILBUR ETAL 2,847,638

VOLTAGE REGULATOR Filed May 27, 1954 2 Sheets-Sheet 1 Fig]. 2

,J VOLTAGE LOAD SOURCE CURRENT In ve r7 tors 0o na/d 14. M/i/buf,

hi/0b H. Peters, Jr.

Aug. 12, 1958 D. A. WILBUR ET AL ,6

VOLTAGE REGULATOR Filed May 27, 1954 2 Sheets-Sheet 2 :7 vomms sat/Rae'-LOAD VOLTAGE LOAD SOURCE VULTH 65 SOURCE II) V en tors: Dona/d A. Wi/bur, hi/l}? hf Peter; J11,

b 7 4. f eir Attorney- United States Patent VOLTAGE REGULATOR Donald A.Wilbur, Albany and Philip HrPeters, :lrqSchenectady, N. Y., assignors toGeneral Electric Company, a corporation of New York Application May 27,1954, 'se'rial No. 432;634 Claims. (Cl. 323-29) This invention rel-atesIto voltage regulators utilizing an oscillator.

Diode devices-are often employed to regulate theciut- :put'volt'age'of arectifier or other direct current voltage supply and may contain anionizable gas. The degree of ionization 'varies with the-voltageimpressed across the diode so that when the diode is connected acrosstherectifier o'utput terminals, "any tendency of the voltage toincreaseuesults in an in'crease'd current flow through the ition, thegaseous type regulator generally requires a startsingvolta'ge higherthan the operating voltage o f'the source which it 're'gula'tes.

It is an=object of thi's invention -to. provide an-iinp'roved voltageregulator.

It is a further object of this invention to provide a woltageiregul'ator having a voltage-current characteristic which is stableoverwide temperature ranges and with :respeotito a wide range of' ripplefrequen'cie's.

.:It is a further object of this invention 'to -provide'an -improvedvoltage regulator employing a diode discharge device "having areadilyadjus'table voltage regulating level.

in accordancewith' this invention a magnetron oscillator is connectedacross the terminals'of a voltage sup .ply having :a resistor :in seriestherewith. Due to the low dynamic resistance 'of the magnetronos'cill'ator When unloaded it operams very effectivelyes adioderegulator. As is well known, the anode tocatho'de voltage required to:start and sustain oscillations is determined by the oscillatingfrequency, the physical geometry of the magnetron device and'themagnetic fieldstrength. By varying the magnetic field strength or thefrequency of oscillatiomthe magnetron operating voltage and hencetheregulating level is readily varied over awide range of values.

The novel features which are believed to be charac'teristic of theinvention are set for'th 'With particularity in the appended claims. Theinvention itself, however, together with "further objec'ts andadvantages thereof can best be -understoo'd byreference to the followingdescripticn taken in connection with the accompanying drawings in which:Figure 1 represents a basic regulating 'circuit incorpora'ting ourinvention. Figure 2 is a curve of the variation of :direct currentvoltage as a function of direct current for atraveling Wave magnetron;Figure 3 is aperspe'ctive view of atype of magnetron which may beemployed in the circuit'of Figure 1'; Figure 4'illustrat'es adifferential connection for magnetron voltage regulators; Figure 5illustrates a parallel connection for magnetron voltage regulators;Figure 6 illustrat'es a cascade connection fo'rniagnetron voltageregulators; and'Fi'gure 7 illusice trates a modified magnetron voltageregulator circuit "having feedback m'eansfor'varying .the magnetronmagnetic field. g Figure lshoivs terminals 1 andlconneeted to directcurrent voltage source 3. Source 3.rnay be 'a rectifier "subject 'toripple or other'voltagefluctuations. .-A regusource voltage is dividedbetween resistorjd anc l-load 5.

The resistor4 may'also be considered tofin clude the internal resistanceof the 'voltage'source. The regulator fiis a traveling wave magnetronhaving an elongated thermionic cathode 7 "connected to the negativeterminal 1 and'a split'a'node 8 eonn'ectedto'the positive terminal 2.Forsirnplicity of illustration, the magnetron anode 8 is sem ischeniatically illustrated 'as having two segments Which'surround"cathode 7 to form a cylindricalspace charge chamber. An 'iinloadedresonant output circuit 9'is connected between the anode segments.Solenoid ;"10 provides an axially directed magnetic field through -thespace chargefichamber. Theterminals .of solenoid 10 are connected to anadjustable direct current ivoltage source "11. A suitable source 'of"heater current1 2 is connected to cathode 7. I v

The magnetroni's operated 'as a conventionaltitraveli-ng wave type withthe'direct current radialelectric fielda-nd the axial magnetic field inthe space charge chamber acting upon the-electronic space chargesothatitassumes an average angular velocity about the cathode. When theelectronst'ravers'ing a gap'between adjacent anode segments are in'phasewith the fringing .alternatingelee tric field between the segments theyreinforce the oscilbut the resonant outputcircuit,beinggunloaded.;substantiaIly'fiXe's the'ope'rating frequency so thatonce the oscillations established by the initial excitation .of thetuned circuit 9'by giving up part of their kinetic energy to thealternating "electric field. Upon losing some of their energy theelectrons move toward the anode ,to regain energy, being eventuallycollectedthere. In this Way the space'charge envelopeis caused to assumea spoke-shaped form, each spoke corresponding to a region of insphaseelectrons having aniaverage angul'ar'velocity synchronous with the;highfrequency electric field of the anode assembly. This is customarilyterr'ned 1r mode e utitation.

An increase 'inthe applied radial electricifield tends to increase theaverage angular velocity 'abovei synchronisin,

lation threshold is reached, a 'further increase in the applied voltagebetween the anode-and cathode results only'ina larger electrondirectcur'rntbeing collected at the anode.

Atypical characteristic curve of direct current voltage as a function ofdirect "current for a traveling wave type magnetron 'is shown in Figure2 as substantially flat for currentvalues above 'the knee of theoperating curve. The voltage drop across the magnetron is substaiitiallyconstant over a wide range of c urrentthrough the magnetron so thatwhenop'erating above the knee of the curve the dynamicres'istance ofthemagnetron diode may be'consider'ed to be very low. The dynamicresistance of a device ma be defined'as the quotientcf an incrementalchange in volitage across the device divided by theresulting incrementalchange .incurrent through the device and may also be defined by'the expression .Dynamic resistanc The magnetron is designed, as isconventional, so as not to be emission limited Since the oscillationthreshold occurs at the knee of the curve and is dependent upon theratio of the radial electric field mine axial 3 magnetic field, themagnetic field density may be adjusted by varying the voltage of thesource 11 to adjust the magnetron operating level. The operating voltagemay also be varied by changing the resonant frequency of theoutput'circuit 9. In orderto maintain a low value ofdynamic resistance;the output circuit 9 is tuned and broadening of its tuning is preventedby maintaining a the output circuit unloaded It may beseen, by referringto Figure 1, that when the voltage of the source 3 tends to rise to avalue above the knee of the curve of Figure 2, the magnetron currentincreases very rapidly, thereby increasing the current through theresistor 4. The increased current through resistor 4 increases thevoltage drop across resistor 4 and tends to maintain a nearly constantvoltage across terminals 1 and 2. Since the magnetron oscillationfrequency is in the order of megacycles, the magnetron dynamicresistance remains essentially constant 'over a frequency range fromzero cycles per second up to frequenciesin the order of megacycles persecond. At high frequencies the sharpness of tuning of the outputcircuit no longer will allow the anode current to build up in the sameratio to the anode voltage as it does at lower ripple frequencies sothat the curve of Figure 2 is no longer substantially flat. In thisrespect, the magnetron voltage regulator is superior to the conventional:gas diode in which the dynamic resistance usually increases rapidly toa very high value at only a few hundred cycles per second. Therefore, nobypass arrangements are necessary to accoimmodate high fre quencyvoltage source changes.

The magnetron reaches its operating voltage smoothly without requiring abreakdown from a higher voltage. The long time stability of themagnetron regulator is also superior since, as a high vacuum device, itis not subject to changes of gas conditions as may occur in gaseousregulators or is it sensitive to temperature variations. Furthermore,the regulating level can easily be adjusted over a wide range bychanging the density of the axial magnetic field.

Figure 3 shows a miniature type low cost magnetron which may be suitablyemployed as the magnetron 6 of Figure 1. This magnetron is of theinterdigital type having two interleaved sets of anode vanes which areconnected by an inductive metal loop. The loop and any vane-to-vanecapacity form an internal tank circuit. For details of constructionalfeatures of small low cost magnetrons of this general type, reference ismade to U. S. Patent 2,617,956, issued November 11, 1952 to L. U. Hamvasand assigned to the assignee of the present invention.

metal disks or rings 16 and 17 spaced in parallel planes along a commonaxis transverse with the lengthwise axis of the tubular envelope. Eachof the annular disks or rings has a similar plurality of digitalprojections which are bent to extend in an axial direction towards theopening in the opposite anode ring. In the example shown, the anode ring16 has a set of four such equally spaced projections 19 which areinterleaved with but spaced from the corresponding set of fourprojections 18 integral with the other anode ring 17. These projectionsare the anode vanes or segments and define a substantially cylindricalspace charge chamber between their inner surfaces. An insulating spacerdisk 20, constructed of a suitable insulating material such as mica, issecured to the outer surface of the anode ring 16, preferably by 4 tabs,and is apertured to receive and support the free ends of the vanes 18extending from the opposite anode ring 17. A similar disk 21 is securedto the anode ring 17 and is similarly apertured to receive and supportthe ends of the anode segments 19. This construction permits the desiredequal spacings between the adjacent anode segments to be maintained.

A cylindrical cathode sleeve 22 is axially positioned in insulatingrelation with the anode segments 18 and 19 by central openings in thespacer disks 20 and 21 through which the cathode ends extend. Thecathode sleeve, which is suitably made of nickel, is coated with athermionically emissive substance, such as barium oxide, which emitselectrons when heated by element 23 positioned within the cathode sleeveto provide the magnetron space charge. The right-hand end of the cathodesleeve is preferably closed to reduce heat losses by radlation and isconductively supported by a lead-in conductor 24. The ends of the heaterare brought out through the open left-hand end of the cathode sleeve andare suitably welded to the internal ends of lead-in conductors 25 and26.

The resonant output circuit for the magnetron is provided by aconductive loop 27 having its ends attached to the anode end rings 16and 17. In the device of Figure 3, this loop is positioned within theenvelope and made of a relatively stiff conductor extending toward thebase of the device. A lead-in conductor 28 is welded or otherwise firmlysecured to the midpoint of loop 27 to support the electrode assembly andprovide a direct current anode connection. No high frequency anodecoupling means or terminals are required since the output circuit ispreferably unloaded to keep the dynamic resistance between the anode andcathode at a minimum value. It is to be understood that while the loop27 has a small inductance, which is all that is needed for the highoperating frequencies for which magnetrons of this type are customarilydesigned, the output circuit may be provided with additional turns forgreater inductance as may be desired for lower frequency operation orwith means for varying the inductance.

The device is conventionally evacuated and sealed. An inductive loopincluding a strip 29 is supported from one of the lead-in conductors. Asuitable getter such as barium is placed on strip 29. After the finalevacuation and sealing of, the envelope, the loop may be excited byinduced high frequency energy to heat and vaporize the getter materialand thus absorb any residual gases remaining in the envelope.

Also shown in Figure 3 is an annular permanent magnet 30 surrounding theenvelope 13, the magnet being notched and magnetized to define thedissimilar poles poles facing opposite ends of the space charge chamber.Electromagnetic means may, of course, be alternatively or additionallyprovided for establishing the axial magnetic field in the space chargechamber.

It is to be understood that various other types of magnetronconstructions may be employed in arrangements embodying our invention.For example, a traveling wave magnetron having an anode block withcavity resonators incorporated therein may be employed. The hole andslot type of cavity resonator is a typical arrangement in this type ofconstruction, the anode segments defined between adjacent slots beinginterconnected by the material of the anode block; therefore, no outputcoupling means is necessary if a cavity resonator type of magnetron isutilized as a voltage regulator.

While magnetrons may readily be designed for operation at relativelyhigh direct current voltages, it may be more convenient where a lowvoltage is to be regulated or where the size of available magnetronsdoes not permit operation at a desired low voltage, to utilize twodifferentially connected magnetrons. Figure 4 shows a first droppingresistor 4 and magnetron 6, series connected, as in Figure 1, across theoutput termmal' set the voltage source 3 and a seconddropping resistor4' and a'second magnetron '6' connected across the outputterminals-ofsource 3. The magn etrons have. different operating characteristics.or are provided with different magnetic field strengths in their spacecharge chambers so that they have operating voltages differing 'by thedesired output voltage.

The'load circuit is connected to the respective output circuits of thetwo magnetrons for low 'voltage operation. tltirnay alsobeseenthatrbyavarying the operating voltage of one or .bothmagnetrons,the differential output voltage may not only be reduced 'to zero but itspolarity may tbexreversed ..as may be desired for certain applications.

It is to be understood that two or more magnetrons may be operated inparallel so that their combined dynamic impedance or resistance isdecreased, thus providing a curve of voltage as a function of currenthaving a lesser slope than the slope of the curve shown in Figure 2.Figure 5 illustrates, by way of example, a circuit arrangement utilizingparallel operated magnetrons. Likewise, a number of magnetron regulatorsmay be operated in cascade, as illustrated in Figure 6, with eachcascade unit having its own voltage dropping resistor 4 and 4'respectively. In Figures 5 and 6, components which are similar to thosein Figures 1 and 4 are identified by the same reference numerals.

The magnetron regulator may be made more sensitive to changes in thevoltage source and to changes in the load by passing the anode currentthrough a solenoid so positioned that it decreases the axial magneticfield in the magnetron as indicated in the circuit of Figure 7. Here, asin Figure 1, a magnetron 6 is connected with its output circuit 9through a resistor 4 to the terminals of a voltage source 3 to beregulated. The magnetic field provided by a solenoid 10 is adjusted toprovide the desired normal magnetron operating voltage. A firstauxiliary solenoid winding 31, which is positioned to produce a magneticfield aligned with that produced by the solenoid 10 is connected inseries between the magnetron 6 and the voltage source 3. The solenoid 31is connected so as to decrease the total magnetic field when the anodecurrent increases. The solenoid 31 is connected between the anode outputcircuit 9 and the dropping resistor 4. A second solenoid 32, alsopositioned to oppose the flux of the solenoid 10, is connected in serieswith the load 5, the load circuit being connected across the magnetronbut not including the solenoid 31.

Solenoid 31 has the effect of decreasing the slope of the characteristiccurve of Figure 2 so that the operating voltage is very little higher athigh current values than the voltage at the knee of the curve. Thus,when the voltage of the source 3 increases, as may be caused by avoltage ripple, the magnetron draws more current and increases thevoltage drop across the resistor 4. At this high value of current thevoltage across the magnetron tends to increase. The increased currentthrough the solenoid 31 results in a decrease in the total magneticfield through the magnetron space charge chamber. Accordingly, a lesserelectric field is required for oscillation, and the voltage across themagnetron tends to decrease so that the over-all curve of voltage as afunction of current tends to be flatter for current values above theknee of the curve. In a like manner, a change in the load current has asimilar effect in that an increase in load current in solenoid 32 lowersthe magnetic field and results in a flatter over-all curve of voltage asa function of current.

From the foregoing, it is to be seen that in accordance with ourinvention a traveling wave type magnetron is very effectively employedas a voltage regulator device in various voltage regulating circuits. Itoperates very effectively to regulate voltages over a wide frequencyrange of voltage fluctuations and the regulating characteristics aresubstantially independent of temperature. The

magnetic field strength can readily be adjusted to change the operatingvoltage to any desired value over a wide range. 'The changes in-theanode current drawn by the magnetron as a regulator cause very littlechange in the operating voltage, particularly so long as the magnetronoutput circuit is unloaded andthe radio frequency power generated bythemagnetron is not externally dissipated.

'Wliile the present inventionhas been described by reference toparticular embodiments thereof,it will be-understood that numerousmodifications may be made by those skilled in the art without departingfrom the invention.

What'we claim as new and desire to secure by Letters Patent 'of theUnited States is:

I. A voltage regulator comprising'a source ofvoltage to be regulated, amagnetron discharge device having a cathode and an anode electrode, aresonant output system including said anode electrode, means forproducing a magnetic field along the space between said anode andcathode, an impedance, means coupling said cathode and said anoderespectively through said impedance to said voltage source to produce anelectric field between said cathode and said anode and operate saidmagnetron at the resonant frequency of said output system whereby thelow dynamic resistance of the magnetron causes a large current changetherethrough corresponding to relatively small voltage changes in saidsource to obtain a regulated voltage across said discharge device havinga magnitude determined by the strength of said magnetic field and theresonant frequency of said output system.

2. A voltage regulator comprising a source of voltage to be regulated, amagnetron discharge device having a cathode and an anode, an unloadedresonant output system including said anode, means for producing amagnetic field along the space between the cathode and anode, animpedance, means coupling said cathode and said anode respectivelythrough said impedance to said voltage source to provide an electricfield between said cathode and said anode and operate said magnetron atthe resonant frequency of said output system whereby the low dynamicresistance of the unloaded oscillating magnetron causes a large currentchange therethrough corresponding to relatively small voltage changes insaid source to obtain a regulated voltage across said discharge devicehaving a'magnitude determined by the strength of said magnetic field andthe resonant frequency of said output system.

3. A voltage regulator comprising a source of direct current voltage tobe regulated, a magnetron discharge device having a cathode and ananode, an unloaded resonant output system including said anode, meansfor producing a magnetic field along the space between the cathode andanode, an impedance, means coupling said cathode and said anoderespectively through said impedance to said voltage source to provide anelectric field between said cathode and said anode and operate saidmagnetron at the resonant frequency of said output system whereby thelow dynamic resistance of the unloaded oscillating magnetron causes alarge direct current change therethrough corresponding to relativelysmall voltage changes in said source to obtain a regulated directcurrent voltage across said discharge device.

4. Means for regulating the voltage between a pair of terminalscomprising a first magnetron oscillator including an anode, a cathode,and a first unloaded resonant output circuit including said anode, avoltage dropping impedance means for coupling a source of direct currentenergy to be regulated across said first magnetron oscil lator through avoltage dropping impedance to produce an electric field between saidcathode and said anode and operate said magnetron oscillator at theresonant frequency of said first output circuit, a second magnetronoscillator including an anode, a cathode and a second unloaded resonantoutput circuit including said anode, a second voltage droppingimpedance, and means for coupling said second magnetron across saidfirst magterminals comprising, a first magnetron oscillator including ananode, a cathode and a resonant output circuit including said anode,means for producing a magnetic field along the space between said anodeand cathode, an impedance, means for coupling a source of energy to beregulated to said first magnetron through said impedance to produce anelectric field between said cathode and said anode and operate saidmagnetron at the resonant frequency of said output circuit, a secondmagnetron oscillator including an anode, a cathode and a resonant outputcircuit, a second impedance, said second magnetron oscillator beingcoupled across said first magnetron oscillator through a secondimpedance to obtain a regulated voltage output.

References Cited in the file of this patent UNITED STATES PATENTS2,750,555 Kather et al June 12, 1956 FOREIGN PATENTS 169,889 GreatBritain Oct. 13, 1921 627,335 Germany Mar. 13, 1936

